RESUMEN
Free metal ion concentrations have been recognized as a better indicator of metal bioavailability in aquatic environments than total dissolved metal concentrations. However, our understanding of the determinants of free ion concentrations, especially in a metal mixture, is limited, due to underexplored techniques for measuring multiple free metal ions simultaneously. In this work, we performed statistical analyses on a large dataset containing repeated measurements of free ion concentrations of Cu, Zn, Pb, Ni, and Cd, the most commonly measured metals in seawater, at five inshore locations in Boston Harbor, previously collected using an in-situ equilibrium-based multi-metal free ion sampler, the 'Gellyfish'. We examined correlations among these five metals by season, and evaluated effects of 10 biogeochemical variables on free ion concentrations over time and location through multivariate regressions. We also explored potential clustering among the five metals through a principal component analysis. We found significant correlations among metals, with varying patterns over season. Our regression results suggest that instead of dissolved metals, pH, salinity, temperature and rainfall were the most significant determinants of free metal ion concentrations. For example, a one-unit decrease in pH was associated with a 2.2 (Cd) to 99 (Cu) times increase in free ion concentrations. This work is among the first to reveal key contributors to spatiotemporal variations in free ion concentrations, and demonstrated the usefulness of the Gellyfish sampler in routine sampling of free ions within metal mixtures and in generating data for statistical analyses.
Asunto(s)
Monitoreo del Ambiente , Estuarios , Metales Pesados/análisis , Agua de Mar/química , Contaminantes Químicos del Agua/análisis , Boston , Monitoreo del Ambiente/métodos , Monitoreo del Ambiente/estadística & datos numéricos , Iones/análisis , Estaciones del Año , Análisis Espacio-Temporal , Temperatura , UrbanizaciónRESUMEN
Free metal ions are usually the most bioavailable and toxic metal species to aquatic organisms, but they are difficult to measure because of their extremely low concentrations in the marine environment. Many of the current methods for determining free metal ions are complicated and time-consuming, and they can only measure 1 metal at a time. The authors developed a new version of the "Gellyfish," an in situ equilibrium-based sampler, with significantly reduced equilibration time and the capability of measuring multiple free metal ions simultaneously. By calibrating the Gellyfish to account for its uptake of cationic metal complexes and validating them in multi-metal competition experiments, the authors were able to determine free metal ion concentrations previously collected over 10 mo at 5 locations in Boston Harbor for Cu, Zn, Pb, Ni, and Cd. This generated 1 of the largest free metal ion datasets and demonstrated the applicability of the Gellyfish as an easy-to-use and inexpensive tool for monitoring free ion concentrations of metal mixtures in marine ecosystems.
Asunto(s)
Ecosistema , Monitoreo del Ambiente/métodos , Metales/análisis , Agua de Mar/análisis , Contaminantes Químicos del Agua/análisis , Contaminación Química del Agua/análisis , Algoritmos , Calibración , Equipo Reutilizado , Reproducibilidad de los Resultados , Manejo de EspecímenesRESUMEN
Contaminant concentrations were determined for media associated with 13 Florida seagrass beds. Concentrations of 10 trace metals were more commonly detected in surface water, sediment and two seagrass species than PAHs, pesticides and PCBs. Concentrations of copper and arsenic in surface water exceeded Florida aquatic life criteria more frequently than other trace elements. Total organic carbon, mercury, chromium, zinc, total chlordane, total PAHs, total PCBs, DDD and DDE were significantly greater in seagrass-rooted sediments than adjacent non-vegetated sediments. Total DDT, DDD, DDE, total chlordane, arsenic, copper and nickel exceeded proposed sediment quality guidelines at six of 13 grass beds. Pesticides, PAHs, and PCBs were below detection in seagrass tissues. Mercury, cadmium, nickel, lead and silver were detected in 50% or more of the tissues for Thalassia testudinum (turtle grass) and Halodule wrightii (shoal grass). Spatial, interspecific and tissue differences were usually an order of magnitude or less.
Asunto(s)
Monitoreo del Ambiente/métodos , Contaminantes Ambientales/análisis , Metales/análisis , Compuestos Orgánicos/análisis , Residuos de Plaguicidas/análisis , Clordano/análisis , DDT/análisis , Diclorodifenil Dicloroetileno/análisis , Diclorodifenildicloroetano/análisis , Ecosistema , Florida , Sedimentos Geológicos/química , Poaceae , Bifenilos Policlorados/análisis , Hidrocarburos Policíclicos Aromáticos/análisis , Contaminantes Químicos del Agua/análisis , HumedalesRESUMEN
The bioavailability of potentially toxic metals in aquatic systems is frequently related to the dissolved free metal ion (M2+) concentration. However, typical methods used to determine M2+ are labor intensive or require sophisticated equipment. We developed an inexpensive, in situ sampling device--the "gellyfish"--that simplifies Cu2+ determinations in seawater. The gellyfish is a thin disk of polyacrylamide gel embedded with iminodiacetate (Id) groups bound to immobile beads. The sampler operates on the principle that the immobilized Id groups equilibrate with the Cu2+ concentration of the surrounding solution. Cu is then back-extracted into a known volume of 10% HNO3 and measured by inductively coupled plasma mass spectrometry (ICP-MS). In laboratory tests, we varied Cu2+ concentrations between 10(-12) and 10(-8) M and salinity between 5 and 35 ppt. Id-bound Cu (CuId(measured)) did not respond to changes in total Cu. However, CuId(measured) does increase in a predictable manner with increasing Cu2+, and prototype gellyfish precision (average coefficient of variation = 10%) is sufficient to resolve small differences in Cu2+ (+/-30%). Modeled Cu uptake, based on thermodynamic equilibrium speciation of Id within gellyfish, is a good predictor of CuId(measured) (r2 = 0.96 and n = 45).